Equipment for the continuous production of foam boards is known and is used for the production of continuous foam buns or sandwich boards which generally consist of a foam core and one or more facings adhered thereto. Double conveyor belts are used to produce such sandwich boards and generally require both a lower and upper conveyor. In the case of foam bun production, the foaming mixture is allowed to freely rise and may be optionally leveled from the top to avoid bulging. In the case of foam sandwich board production, the two conveyors put pressure on the foaming mixture. One problem facing the art, which has not yet been satisfactorily solved, is the continuous distribution of the reaction mixture in the advance and the transverse directions.
One commonly used method is to use an application device having a mixhead which moves transversely back and forth. This method, however, causes the foaming material to accumulate at the edges. The oscillating movement of the mixhead causes high impacts on the turning points. Because of the required high velocity, these impacts create wear and tear and cause the foamable material to splash. At high manufacturing velocities, the additional problem occurs that the distance between the zigzag lines of the applied foamable mixture becomes too great for uniform foaming.
The use of an inclined table is also well-known in the art. It has the advantage that the foaming reaction mixture flowing from the mixhead meets the application surface more gently due to the angle of inclination. The mixture partially distributes itself over the width on the table. With wider widths, several parallel mounted mixheads have been used. Difficulties are, however, often encountered at the points where the individual flows intermix during spreading. Cellular striation and bubbles will then generally form in the finished part.
Attempts have been made to level the applied mixture with a rake or a roller which forms a space or gap with the lower conveyor surface. Problems have, however, been encountered when the height of the space or gap is too high. It was found that the transverse distribution did not take place fast enough and that the reaction mixture begins to foam on the edges before it passes through the space or gap. This causes nonhomogeneous edge zones, which vary in structure as well as in density. For these reasons, the processing of foaming materials, particularly of highly reactive systems, presents considerable problems.
Therefore, in the continuous production of continuous foam buns and particularly in the production of foam boards or sandwich boards having a foam core, the problem of improving the mixture distribution over the operation width to such a degree that a satisfactory homogeneity of the finished part is obtained, must be solved. In doing this, the length of the pouring end and the total length of the equipment should be as short as possible.